Tire uniformity correction without grinding

ABSTRACT

A method and apparatus for reducing the magnitude of a uniformity characteristic in a cured tire and the tire produced thereby. A signal is generated which is indicative of the magnitude of the uniformity characteristic. The signal is also indicative of the location on the tire to be corrected. At least a portion of one carcass reinforcing member of the tire is permanently deformed a predetermined amount at the location indicated by the signal to correct the uniformity characteristic.

This application is a division of application Ser. No. 08/303,228, filedon Sep. 8, 1994, now U.S. Pat. No. 5,458,176, which was a division ofSer. No. 07/863,256, filed Apr. 3, 1992, now U.S. Pat. No. 5,365,781.

BACKGROUND OF THE INVENTION

1. Technical Field

The present invention relates generally to a pneumatic vehicle tire, andto a method and an apparatus for correcting at least one uniformitycharacteristic in the tire. In particular, the present invention relatesto correcting the uniformity characteristic in the tire, such as radialforce variation and/or conicity, without grinding any part of the tire.

2. Description of the Prior Art

It is known in the tire industry that it is difficult to manufacture atoroidal shaped pneumatic radial tire consistently the same every timefrom sheet and/or strip material. A typical pneumatic radial tireincludes a pair of axially spaced apart and circumferentiallyinextensible beads. A carcass ply extends between the beads and isattached to a respective bead at axially opposite end portions of thecarcass ply. The carcass ply includes a plurality of parallel extendingreinforcing members. The carcass ply is formed into a toroidal shape andhas a belt package located radially outward of the carcass ply in acrown portion of the tire. Tread rubber and sidewall rubber are appliedover the belt package and carcass ply, respectively.

After the tire is assembled and cured, the tire is typically tested fora uniformity characteristic. "Uniformity" is defined herein as what a"perfect" or "ideal" tire would yield for certain measuredcharacteristics when tested during rotation. "Uniformity characteristic"is defined herein as a deviation in those certain characteristics fromwhat the perfect tire would yield during the testing.

Testing a tire for a uniformity characteristic typically begins withmounting the tire in a inflated condition on a test spindle of auniformity tester. A test wheel is moved into engagement with the tireto radially deflect a portion of the tire a predetermined amount. Theposition of the axis of rotation of the test wheel relative to the axisof rotation of the tire is then fixed by a locking mechanism. The testwheel is rotated to cause rotation of the tire. Sensors associated withthe test wheel sense radial and lateral loads transmitted by the tire tothe test wheel during rotation of the tire.

One uniformity characteristic test which is generally performed on thetire is a test for radial force variation. Radial force variation istypically expressed as a variation in the force against the test wheelwhich is sensed during rotation of the tire. Radial force variation canbe represented by a combination of first harmonic radial force variationthrough an Nth harmonic radial force variation or a composite radialforce variation. The Nth harmonic is the last harmonic in a FourierSeries analysis of the composite radial force variation which is deemedacceptable to accurately define the radial force variation. It is knownin the tire and automobile industries that vehicle ride is generallymost affected by the first harmonic radial force variation of the tire.The first harmonic radial force variation is often associated with"radial runout" of the tire. Radial runout is defined as a difference inthe radius from the axis of rotation to the outer periphery of the tiretread around the tire.

Another uniformity characteristic test which may be performed on thetire is a test for conicity. Conicity is defined as the tendency of arotating tire to generate a lateral force regardless of the direction ofrotation of the tire. Conicity is expressed in terms of average lateralforce generated during rotation in both directions of the tire againstthe load.

Such uniformity characteristics may be attributed to the manufacture ofa tire from the sheet and/or strip material. The uniformitycharacteristics can simplistically be viewed as a deviation from perfectroundness of the outer circumference of the tire, as deviation fromspindle load transmitted by a perfect tire during rotation (radial forcevariation) or as deviation from straight tracking during rotation(conicity). For example, the tread rubber of the tire may be thicker orthinner in one location around the outer circumference of the tire.There may also be areas of the tire having increased strength because ofa doubling of a tire reinforcement, such as at the splice from sheetcarcass ply material. Lack of bead concentricity of the tire may also bea problem. The beads of the tire may be not exactly concentric relativeto the axis of rotation of the tire or the tread may not be concentricwith the beads (radial runout). The carcass ply of the tire may besubjected to more or less localized stretch of the carcass reinforcingmembers during assembly of the tire. The molding and curing processes ofthe tire assembly could also create localized stretching of the carcassreinforcing members. The belt package of the tire may be axiallydisplaced or conically shaped.

If the uniformity characteristic of the tire has a magnitude which isless than a predetermined relatively low minimum magnitude, which isdeemed not to be detrimental to a vehicle ride or produce undesirablevibrations in the vehicle, the tire may be shipped to a customer. If theuniformity characteristic magnitude is greater than a predeterminedmaximum threshold magnitude, the tire is scrapped. If the uniformitycharacteristic magnitude is between the relatively low minimum magnitudeand the maximum threshold magnitude, the tire may be suitable forcorrection.

Typically, prior art correction of a uniformity characteristic of atire, such as radial force variation, included grinding of tread rubberabout the outer circumference of the tire at a selected location and upto 180 degrees about the outer circumference of the tire. However,grinding of the tire has certain disadvantages. For example, grindingcan contaminate a tire plant environment, reduce the useful tread lifeof the tire or may render the tire visually unappealing. Prior attemptsat correcting a pneumatic tire uniformity characteristic withoutgrinding are disclosed in U.S. Pat. Nos. 3,529,048; 3,632,701;3,838,142; 3,872,208; 3,880,556; 3,945,277 and 5,060,510.

U.S. Pat. No. 3,529,048 discloses placing a tire on a fixtureimmediately after the tire is removed from a mold and before it iscooled. The tire is inflated to its recommended operating pressure. Aradial load is applied to the tire and the tire is rotated for a time atleast equal to the tire cure time. The flexing of portions of the tireallow components or portions of the components of the tire to"relatively move" before the tire is completely cured to yield uniformstresses in the components.

U.S. Pat. No. 3,632,701 discloses heating a tire after curing to atemperature elevated above an ambient temperature. The elevatedtemperature is maintained for about sixty minutes while the tire isinflated to a pressure of up to 50 psi. This obviously has drawbacks ina modern tire production plant because of the relatively long timerequired to correct the uniformity characteristic of the tire comparedto a cure cycle time of less than thirty minutes for a passenger carradial tire.

U.S. Pat. No. 3,838,142 discloses subjecting selected sections of thetire to radiation to increase the modules of elasticity of thosesections. U.S. Pat. Nos. 3,872,208 and 3,880,556 disclose applying heatto a portion of the inner surface of the tire. U.S. Pat. No. 3,945,277discloses applying heat to the tire sidewalls during rotation of thetire in contact with rollers in order to "condition" the tire.

U.S. Pat. No. 5,060,510 discloses correcting radial force variation of atire and rim assembly without grinding the tire tread. A pair ofcircumferential shims are placed between respective tire bead areas andmounting areas of the rim as a function of the measured radial forcevariation. Each shim has a varying thickness over its circumference. Fora flat seat rim, the largest thickness portion of the shims are placedat the location of the largest amplitude of the radial force variation.

SUMMARY OF THE INVENTION

The present invention is directed to correcting a uniformitycharacteristic, such as radial force variation or a conicity, in a fullycured pneumatic tire and particularly in a radial pneumatic tire. Themethod and apparatus of the present invention accomplishes suchcorrection without the drawbacks of the prior art methods which can beenergy inefficient, costly and/or time consuming. The present inventionis, thus, directed to an apparatus and a method for correcting at leastone uniformity characteristic in the tire in a relatively short periodof time and without grinding. The present invention is also directed toa tire resulting from the uniformity characteristic correction by suchmethod and apparatus.

The method embodying the present invention is for correcting auniformity characteristic in a cured tire. A signal is generated whichis indicative of the magnitude of the uniformity characteristic and ofthe location on the tire to be corrected. A portion of at least onecarcass reinforcing member is permanently deformed a predeterminedamount as a function of the location and magnitude indicated by thesignal.

The apparatus embodying the present invention for correcting auniformity characteristic comprises means for generating a signal whichis indicative of the magnitude of the uniformity characteristic and ofthe location on the tire to be corrected. The apparatus includes meansfor permanently deforming at least one carcass reinforcing member apredetermined amount as a function of the magnitude and location of theuniformity characteristic indicated by the signal to provide thecorrection.

Correction of the tire is typically performed when the magnitude of theuniformity characteristic is within a predetermined range of magnitudes.The reducing step and/or means preferably includes stretching at least aportion of the carcass reinforcing member beyond its elastic limit for apredetermined time. The stretching results in a permanent lengthening ofthe carcass reinforcing member as a function of the magnitude of theuniformity characteristic, but preferably by at least 0.1 percent.

The magnitude of the uniformity characteristic varies circumferentiallyaround the tire as given by the signal. Stretching the carcassreinforcing members for proper correction must also varycircumferentially around the tire. Variable stretching is associatedwith a means for providing a variable tension in the carcass reinforcingmembers. This can be achieved by a tension applied to each individualcarcass reinforcing member or by a method of restraining the tire andconcurrently tensioning plurality of carcass reinforcing members over aside or predetermined angular segment of the tire. The type and amountof restraint is a function of the uniformity characteristic, themagnitude and location of the correction the pressure or force appliedas well as the physical parameters of the tire.

Consider the signal to be indicative of a composite or total radialforce variation. Total radial force variation may be analyzed todetermine the first harmonic radial force variation or a predeterminedother harmonic. A portion of the sidewall of the tire may be restraineda maximum amount at a location 180°, for the first harmonic,circumferentially spaced from the location indicated by the signal and aminimum amount, or not at all, at the location indicated by the signal.The sidewall may be linearly restrained to a gradually lesser amount inboth circumferential directions from the location of maximum restrainttoward the location of minimum restraint. Alternatively, non-linearrestraint may be applied to the sidewall of the tire.

The minimum restraint permits a maximum amount of permanent deformationto at least one carcass reinforcing member at the location of minimumrestraint. A gradually lesser amount of permanent deformation may thenbe provided to other carcass reinforcing members in both circumferentialdirections from the location of minimum restraint to a minimum amount ofpermanent deformation at the location of maximum restraint.

Restraining the sidewall or sidewalls of the tire can be accomplished byan annular restraint device having a planar side surface for engaging anannular portion of the sidewall. The radial length of engagement of therestraint device may be a relatively small percentage of the sectionheight of the tire. Alternatively, another restraint device may beprovided in which the radial length of engagement may be a relativelylarge percentage of the section height of the tire. The orientation ofthe restraint device relative to the mid-circumferential plane of thetire may be varied as a function of the magnitude of the radial forcevariation.

Conicity of the tire may be corrected by permanently deforming a portionof all carcass reinforcing members a substantially equal amount in onlyone sidewall of a tire indicated by the signal. Conicity may also becorrected by permanently deforming a portion of the carcass reinforcingmembers at the side of the tire indicated by the signal by an amountdifferent than the permanent deformation applied to a portion of thecarcass reinforcing members in the other side of the tire.

A method and apparatus for reducing the magnitude of a uniformitycharacteristic in a cured tire is also provided. The location on thetire to be corrected is determined. A pseudo radial runout is introducedto the tire as a function of the location to be corrected in order tooffset the uniformity characteristic and thereby reduce the firstharmonic magnitude of a resulting uniformity characteristic to amagnitude below a minimum threshold.

The corrected tire includes a pair of spaced apart and circumferentiallyinextensible beads. A carcass extends between the beads and has axiallyopposite end portions attached to a respective one of the beads. Thecarcass includes a plurality of parallel extending reinforcing members.At least one of the carcass reinforcing members has a portionpermanently deformed beyond its elastic limit to reduce a uniformitycharacteristic of the tire. The carcass reinforcing members arepreferably made from a polyester material. The tire may include a beltpackage located radially outward of the carcass in a crown portion ofthe tire. The permanently deformed portion of the carcass reinforcingmember is preferably located in a sidewall of the tire. The portion ofthe carcass reinforcing member is permanently elongated by at least 0.1percent.

BRIEF DESCRIPTION OF THE DRAWINGS

Further features of the present invention will become apparent to thoseskilled in the art to which the present invention relates from readingthe following specification with reference to the accompanying drawings,in which:

FIG. 1 is a flow diagram of process operations for testing and analyzingthe uniformity characteristics of a tire;

FIG. 2 is a graphical representation of a composite radial forcevariation of a tested tire as a function of the angular location aroundthe tire;

FIG. 3 is a graphical representation of the initial values of the firstthrough third harmonics of a radial force variation of the tested tire;

FIG. 4 is a graphical representation of composite radial forcevariations of a tire having a first harmonic corrected according to thepresent invention, before and after running of the tire;

FIG. 5 is a graphical representation of the first through thirdharmonics of radial force variation after correction of the firstharmonic of the tire;

FIG. 6 is a elevational view of an apparatus embodying the presentinvention for correcting a uniformity characteristic of a tire;

FIG. 7 is a view of the apparatus in FIG. 6 with parts moved todifferent positions illustrating use of the method and apparatus;

FIG. 8 is a cross-sectional view of a tire mounted in a portion of theapparatus embodying the present invention and illustrating restraint ofthe sidewalls of the tire;

FIG. 9 is an enlarged cross-sectional view of a portion of the tire andapparatus illustrated in FIG. 8;

FIG. 10 is a schematic representation of a sidewall portion of a carcassreinforcing member in FIG. 9, before and after maximum restraint of thesidewall;

FIG. 11 is a cross-sectional view of a portion of a carcass reinforcingmember restrained at two radial locations according to an alternateembodiment restraint ring of the present invention;

FIG. 12 is a graphical representation of permanent elongation of carcassreinforcing members between locations of minimum and maximum restraintof the sidewall in both directions and as a function of angular locationaround the tire;

FIG. 13 is a side view of a tire before and after correctionillustrating the introduction of radial runout of the tire to offset anexisting radial force variation;

FIG. 14 is a flow diagram of the correction method embodying the presentinvention;

FIG. 15 is a cross-sectional view of an alternative embodiment restraintof the tire sidewall;

FIG. 16 is a schematic representation of a portion of a carcassreinforcing member before and after restraining the sidewall accordingto the embodiment illustrated in FIG. 15;

FIG. 17 is a cross-sectional view of another alternate embodimentillustrating stretching a sidewall portion of the carcass reinforcingmember by a mechanism;

FIG. 18 is a graphical representation of the carcass reinforcing memberstretched according to the embodiment illustrated in FIG. 17;

FIG. 19 is a graphical representation of yet another alternateembodiment of the present invention method that illustrates stretching aportion of the carcass reinforcing member by a mechanism;

FIG. 20 is a graphical representation of the behavior of a portion of acarcass reinforcing member stretched as a function of time;

FIG. 21 is a perspective view of the alternate embodiment of a restraintring embodying the present invention for selectively restrainingportions of a sidewall of a tire;

FIG. 22 is a side view of the restraint ring (illustrated in FIG. 11)for varying the amount of restraint around the tire; and

FIG. 23 is a cross-sectional view, similar to FIG. 8, of a tirerestrained by the restraint ring illustrated in FIG. 21.

DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

A radial pneumatic tire 40 for uniformity characteristic correction inaccordance with the present invention is illustrated in FIGS. 8 and 9.The tire 40 is rotatable about a longitudinal central axis A. The tire40 includes a pair of beads 42 which are substantially inextensible in acircumferential direction. The beads 42 are spaced apart in a directionparallel to the axis A. Circumferential is defined as beingsubstantially tangential to a circle having its center at axis A andcontained in a plane parallel to the mid-circumferential plane M of thetire.

A carcass ply 44 extends between each of the respective beads 42. Thecarcass ply 44 has a pair of axially opposite end portions which extendaround the respective bead 42. The carcass ply 44 is secured at theaxially opposite end portions to the respective bead 42. The carcass ply44 includes a plurality of substantially parallel extending reinforcingmembers each of which are made of a suitable configuration and material,such as several polyester yarns or filaments twisted together. It willbe apparent that the carcass ply 44 is illustrated as a single ply butmay include any appropriate number of carcass plies for the intended useand load of the tire 40. It will also be apparent that the reinforcingmember may be a monofilament or any other suitable configuration ormaterial.

The tire 40 illustrated in FIGS. 8 and 9 also includes a belt package46. The belt package 46 includes at least two annular belts. One of thebelts is located radially outwardly of the other belt. Each beltincludes a plurality of substantially parallel extending reinforcingmembers made of a suitable material, such as a steel alloy. The tire 40also includes rubber for the tread 62 and sidewalls 64. The rubber maybe of any suitable natural or synthetic rubber, or combination thereof.

In the tire 40, uniformity characteristics may result from the assemblyand curing operations in a tire plant. For example, the tire 40 istested after curing and cooling for certain uniformity characteristics,such as radial force variation, ply steer and/or conicity. FIG. 1 is aflow diagram of the processes that the tire 40 may undergo after it hasbeen assembled, cured and cooled in operation 82. The tire 40 is placedon a uniformity tester (not shown). The uniformity tester is well knownin the tire manufacturing art. The tire uniformity tester is availablefrom a supplier such as Akron Standard, Akron, Ohio.

The tire 40 is mounted in an inflated condition to its normalrecommended operating pressure on a mounting device which simulates avehicle rim. The tire 40 is then engaged by a test wheel which loads thetire to an appropriate predetermined radial load. The relative distancebetween the axes of rotation of the tire 40 and of the test wheel(center-to-center distance) is then fixed. The test wheel is rotated toimpart rotation to the tire 40. Sensors which are operatively connectedwith the test wheel sense radial force and lateral force variations fromthe load applied to the tire 40 in operation 84. The test parameterswhich may be adjusted for the test include applied load, inflationpressure and rolling radius of the tire 40. The parameters are dependentupon the type of tire 40 and the particular size tire tested. Forexample, test parameters for a 205/70R15 passenger car tire are a 502decaNewtons (daN) load, 30 psi inflation pressure and thecenter-to-center distance fixed when the radial load of 502 daN isreached.

The tendency for the tire 40 to generate a lateral force in a directionalong the axis A during rotation of the tire 40 when loaded against thetest wheel in one direction is also sensed in operation 84. This istermed lateral force variation. The tire 40 is then rotated in theopposite direction and another lateral force variation is sensed. Thesensing of the magnitudes of the lateral force variations and themagnitude around the tire of the radial force variation is performed inoperation 84. In operation 86, the conicity of the tire 40 isdetermined. Conicity magnitude is defined as the average of lateraloffsets when the tire 40 is rotated in one direction and then rotated inthe opposite direction. Lateral offset is defined as the mean of thepeak-to-peak lateral force variation when the tire is rotated in onedirection about its rotational axis when loaded.

In FIGS. 2 and 3 an initial radial force variation of the uncorrectedtire 40, as tested, is graphically illustrated to representcorresponding electrical signals. The radial force variation as afunction of circumferential position on the tire 40 is represented by awave form illustrated in FIG. 2, which may be decomposed into a numberof desired harmonic wave forms, as illustrated in FIG. 3. In operation87 (FIG. 1), the harmonic wave forms are determined in a computer (notshown) by a Fourier analysis of the radial force variation wave formsensed during rotation of the loaded tire 40. In FIG. 3, for clarity ofillustration purposes, only the uncorrected first through third harmonicradial force variations in decaNewtons of force variation from test loadduring rotation of the tire 40 are graphically represented as a functionof angular location around the tire from a reference location. It isapparent that the composite wave form is better represented by a greaternumber of harmonic wave forms. The analysis and wave forms are stored inthe computer and referenced to a particular tire 40 in operation 87.

The composite radial force variation and conicity are typicallydetermined by the tire uniformity tester. Once the conicity and radialforce variation magnitudes are determined, they are compared to arespective minimum acceptable threshold limit in operation 88 (FIG. 1).If the absolute value of the conicity magnitude and radial forcevariation magnitude are less than a respective predetermined minimumthreshold magnitude limit, the tire 40 is deemed acceptable and nofurther processing of the tire is needed. The tire 40 is then typicallyshipped to a customer as indicated in operation 102.

If the tire 40 has a magnitude for conicity (absolute value) or radialforce variation greater than the corresponding acceptable minimumthreshold magnitude limit, another comparison is performed in operation104. If the conicity (absolute value) or radial force variationmagnitudes are greater than a relatively large maximum thresholdmagnitude limit, the tire 40 is deemed uncorrectable. If the tire 40 isuncorrectable it is scrapped in operation 106.

If the tire 40 falls within a predetermined range of magnitudes forconicity (absolute value) and/or radial force variation, it is forwardedfor uniformity characteristic correction in operation 108. For example,if the conicity (absolute value) and/or radial force variationmagnitudes are greater than the acceptable minimum threshold magnitudelimit for shipping to a customer but less than the relatively largemaximum threshold magnitude limit for scrapping, the tire 40 may becorrected at a uniformity correction station. After the tire 40 iscorrected and allowed to sit for a period of time, for example twentyfour hours, it may be again tested as indicated by the dashed line 120.This "sit period" is sufficient time to take into consideration anyviscoelastic relaxation that occurred in the tire 40 after correction.If the corrected tire 40 has uniformity characteristic magnitudes belowthe minimum acceptable threshold limits it is shipped to the customer.If the tire 40 does not have an acceptable uniformity charactermagnitude, it may be scrapped or may be again corrected. Preferably,after the tire 40 is corrected once it will be below the acceptableminimum threshold magnitude limit and shipped to the customer.

A tire 40 that is to be corrected is transported to a correction station140 embodying the present invention, as illustrated in FIG. 6. Thecorrection station 140 includes vertical frame members 132 as well asupper and lower cross members 134. An air tank 136 may be mounted to theupper cross member 134. The mode of transportation of the tire 40 may bemanual or automated on a conveyor system 138. The tire 40 is initiallysupported in the correction station 140 in the position illustrated inFIG. 6. It should be apparent that the correction station 140 could be astand alone operation or be incorporated into a tire uniformity testmachine for a combination test and correct operation.

A lower simulated rim mounting 142 is moved upwardly by a main actuator144 from the position illustrated in FIG. 6 towards the positionillustrated in FIG. 7. The lower simulated rim mounting 142 (FIG. 6) isbrought into axial engagement with the lower bead area 146 of the tire40. The main actuator 144 continues to raise the tire 40 away from theconveyor 138. The tire 40 then is forced against the upper simulated rimmounting 162 at the upper bead area 164, as illustrated in FIGS. 7 and8. The tire 40 is inflated with fluid pressure, such as air, to apressure sufficient to seat the bead areas 146, 164 of the tire 40against the simulated rim mountings 142, 162. Then the tire 40 isdeflated to a relatively low pressure which is above the surroundingambient atmospheric pressure and which pressure is approximately equalto one-tenth the recommended operating pressure of the tire.

Once the tire 40 is located in the correction station 140, aprogrammable controller 166 (FIG. 6) operably connected with thecorrection station 140 and computer determines, in operation 202 (FIG.14) by a variety of inputs, if conicity correction, radial forcevariation correction or both is to be performed. At the tire correctionstation 140 the tire 40 has an indicator, such as a bar code label or aninfrared ink identification which is read and indicates informationabout the tire 40 to the controller 166. Such information may be, forexample, information related to reference measurements (i.e., soft spotor hard spot) or a unique identifier, such as a serial number which iscommunicated to the controller 166. The controller 166 can then inputdata associated with that serial number, such as the type of uniformitycharacteristic to be corrected as well as the wave forms and analysisthat were stored in the computer in operation 87 (FIG. 1). Once thisinformation is known to the controller 166 the tire 40 located in thecorrection station 140 can be corrected.

If the controller 166 and control program determine that radial forcevariation of the tire 40 is to be corrected in operation 202 (FIG. 14),the controller and control program determine which radial forcevariation, composite or harmonic, is to be corrected in operation 208.If for example, an operator or the control program has indicated, inoperation 208, that the first harmonic of the radial force variation isthe desired harmonic to be corrected, operation 220 sets inputparameters, to be used in a later operation, indicating the firstharmonic. Alternatively, operation 220 can be programmed to select theharmonic of the radial force variation to be corrected as a function ofa predetermined parameter, such as the harmonic with the greatestmagnitude. Once it is determined that one or more harmonics of theradial force variation is to be corrected, operation 221 analyzes orreads the stored harmonic wave forms as illustrated in FIG. 3.

If the first harmonic of the radial force variation is to be correctedas determined in operation 220, an analysis of the first harmonic waveform (if it has not been analyzed already) is performed in operation221. The analysis may have already been done in operation 87 (FIG. 1)and stored for use at this time. The analysis will now be described indetail for a better understanding of such analysis. The analysis can bebetter understood with reference to FIG. 3. In FIG. 3, the initial firstharmonic wave form signal for the uncorrected tire 40, as tested, isillustrated. Only two radial force variation input parameters arerequired to initiate the first harmonic correction. The magnitude 238and the location 236 from a reference location provide these parameters.The magnitude is the difference between the soft spot 232 magnitude andthe hard spot 234 magnitude. The location is the angular position 236 ofthe soft spot 232 from the reference. These two parameters are obtainedin operations 221 and 222 of FIG. 14, and/or operation 87 of FIG. 1.

This peak-to-peak magnitude 238 may be graphically represented as, forexample, approximately 4.55 daN, of first harmonic desired correction(FIG. 3). If, for example, the tire 40 has four daN first harmonicpeak-to-peak radial force variation or less, and which four daN may bethe minimum threshold acceptable limit for magnitude, the tire 40 wouldbe shipped to the customer. If the relatively large maximum thresholdlimit for scrapping the tire 40 is greater than or equal to, forexample, 10 daN first harmonic peak-to-peak magnitude, the tire would bescrapped. Here it is apparent that the 4.55 daN approximate peak-to-peakmagnitude 238 of first harmonic radial force variation is within thepredetermined range of peak-to-peak magnitudes of four daN to ten daNand, thus, the tire 40 is suitable for correction.

The analysis operation 221 also includes the location 236 of the firstharmonic soft spot 232 around the tire 40 as an angular position from aphysical reference on the tire 40. Thus, the location 236 of the firstharmonic soft spot 232 is known to operation 222 (FIG. 14). Themagnitude 238 and location 236 of the soft spot are used as inputparameters to determine control parameters for the correction operation258.

Correction of the uniformity characteristic is accomplished in operation258 (FIG. 14) by permanently deforming at least one, and preferablymany, carcass reinforcing members. The stretching is done preferably byapplying relatively high inflation pressure to the interior of the tire40 for a predetermined time. Input parameters are preferably used inoperation 206 to determine control parameters for the correctionoperation 258. The control parameters are known to the controller 166before the correction operation 258 is initiated. The input parameter ofmagnitude 238 affects the determination of control parameters such asdeflection, time and pressure (or force) which are applied to the tire40. The input parameter of location 236 (FIG. 3) of the soft spotaffects the positioning of the tire 40 in the correction station 140.Other input parameters affecting the control parameter such asdeflection, time and pressure applied to the tire 40 include the typeand properties of material of the carcass reinforcing member. An exampleof properties include diameter, pitch and number of filaments used inthe carcass reinforcing member. Materials of the carcass reinforcingmember such as nylon and polyester are readily adaptable to correctionby the present invention. Materials such as steel, Kevlar and rayon arenot as easily permanently elongated and may require higher pressure orlonger hold time.

A signal is generated by the controller 166 which is indicative of atleast the magnitude 238 (FIG. 3) of correction desired and the angularlocation 236 from a reference on the tire 40 to be corrected. The signalmay be hydraulic, pneumatic or preferably electronic. When the tire 40is delivered to the correction station 140, the orientation of the tiremay be accomplished relative to a known location on the correctionstation. For example, as illustrated in FIG. 6 if a first harmonicradial force variation correction is needed the location 236 of thefirst harmonic soft spot 232 is positioned at the far left hand side ofthe correction station 140, as viewed in FIG. 6. This positioning can bedone by first marking the soft spot or relative to the physicalreference of the tire 40 an angular amount equal to the location 236 indegrees.

With the tire 40 properly located and initially inflated, the correctionstation 140 is then further activated to assume the position illustratedin FIG. 7. The correction station 140 includes at least one restraintring 182 which is brought into engagement with at least onecorresponding sidewall of the tire 40. The number and type of restraintrings 182 brought into engagement with the sidewall or sidewalls of thetire 40 is determined as a control parameter in operation 206 as afunction of the type correction desired in operation 258. If the firstharmonic of radial force variation is to be corrected, then both theupper restraint ring 182U and lower restraint ring 182D engage therespective sidewalls of the tire 40.

Correcting a first harmonic radial force variation includes inflatingthe tire 40 to a pressure above the recommended operating pressure ofthe tire 40 as a function of input parameters while restraining aportion of the sidewall to control the distribution of the correctionaround the tire. Stretching and permanently lengthening a portion of thecarcass reinforcing member at different locations around the tire cancorrect the uniformity characteristic of the tire 40. Permanentdeformation or elongation L is achieved by stretching a carcassreinforcing member beyond its elastic limit and holding it for apredetermined time, as illustrated in FIG. 20. The distribution of theamount of lengthening is controlled by restraining the sidewall of thetire 40 by an amount that varies around the circumference of the tire.This varying circumferential stretching is a function of the uniformitycharacteristic being corrected and other parameters.

Restraint rings 182 (FIG. 8) engage the sidewalls with different axialdisplacements D1,D2 to impart a different radius of curvature R1,R2 tothe portion of the carcass reinforcing member 306 (FIG. 9) in each ofthe sidewalls. The restraint rings 182 are used preferably only wheninflation pressure is used for correction. The radius of curvature R2 ina maximally restrained portion of the tire 40 corresponding todisplacement D2 is significantly less than radius of curvature R1 in theminimally restrained portion of the tire corresponding to displacementD1. Different radii of curvature provide different tension values inrespective carcass reinforcing members.

The maximum amount of restraint to be applied for first harmonic radialforce variation correction is at the first harmonic hard spot 234 on thetire 40 at a location 180° away from the location 236 of the firstharmonic soft spot 232 indicated by the signal. The maximum restraintoccurs at the location of maximum axial displacement D2 relative to themid-circumferential plane M of the tire 40 which is to the far right inthe correction station 140, as viewed in FIG. 7. A minimum amount ofrestraint, or no restraint (at all i.e. a gap) is applied to thesidewalls of the tire 40 at the location of the first harmonic soft spot232 indicated by the signal and known to the controller 166 andcorrection station 140. The minimum restraint occurs at the location ofminimum axial displacement D1 relative to the mid-circumferential planeM of the tire 40. This is at the far left of the correction station, asviewed in FIG. 7. More correction to the tire 40 occurs at the locationof minimum restraint and relatively less (or no) correction occurs atthe location of maximum restraint.

FIG. 10 is a schematic illustration of one carcass reinforcing member306 being corrected according to the preferred embodiment of the presentinvention. A portion 302 of the carcass reinforcing member 306 isillustrated in FIG. 10 by a dashed line prior to being restrained. Thisportion 302 of the carcass reinforcing member 306 has an upper end point304 at which load in the carcass reinforcing member is transmitted tothe belt package 46 of the tire 40. The portion 302 of the carcassreinforcing member 306 has a lower end point 308 in the area of the bead42 (FIG. 9) at which load in the carcass reinforcing member istransmitted to the bead of the tire 40. The deflected portions 312 ofthe portion 302 of the carcass reinforcing member 306 are illustrated inFIG. 10 in solid line. The deflection distance 310 is illustrated inFIG. 10 to correspond to the maximum amount of restraint discussed abovein terms of deflection D2.

In the deflected portions 312 of the carcass reinforcing member 306 itwill be apparent that the original or unrestrained radius of curvatureR1 of the carcass reinforcing member has changed and is now a relativelysmaller radius of curvature R2 in two locations. Physically the smallerradius R2 of portion 312, when the interior of the tire 40 is subjectedto the same relatively high inflation pressure, such as 100 psi or 7bars, will not be permanently elongated the same amount as theunrestrained portion 302 of the carcass reinforcing member 306 havingthe relatively larger radius of curvature R1. The relationship betweentension in the carcass reinforcing member 306, radius of curvature inthe reinforcing member 306 and inflation pressure in the tire 40 can berepresented by the formula T=R.P, where T is the tension force in theportion 302 of the carcass reinforcing member 306, R is the radius ofcurvature of the portion 302 or 312 of the carcass reinforcing member306, P is the internal inflation pressure in the tire 40 causing tensionin the portion 302 of the carcass reinforcing member 306. Thus, it willbe apparent that for a constant inflation pressure P, the larger theradius of curvature R of the portion 302 of the carcass reinforcingmember 306, results in a relatively higher the tension T acting on thatportion of the carcass reinforcing member. Thus, the higher tension inthe portion 302 of the carcass reinforcing member 306 generally resultsin a relatively greater elongation above the elastic limit of thematerial which results in permanent elongation. The larger radius ofcurvature R1 in the portion 302 occurs at the location of minimumrestraint around the tire 40 with a planar ring restraint device.

The restraint rings 182 may be of any configuration desired that issuitable for the type correction to be performed and as a function ofthe parameters determined in operation 206. For example, as illustratedin FIG. 8 a pair of restraint rings 182 are brought into engagement withthe sidewalls of the tire 40 from axially opposite sidewall sides. Therestraint difference is accomplished at the correction station 140 byaxially moving the restraint rings 182 different amounts relative to themid-circumferential plane M of the tire 40 at diametrically oppositeregions of the tire. The axial movement of the restraint rings 182 isperformed at the far left and far right in the correction station 140 bytwo pairs of actuators 246 (FIG. 7). The lower restraint ring 182D issupported at diametrically opposed end portions by a pair of actuators246, each of which is driven by a respective motor 244. The loweractuators 246 are movable axially relative to a lower support 242D. Thesupport 242D has the motors 244 attached directly thereto. Uponactuation of one of the motors 244, an associated actuator 246 moves thelower restraint ring 182D axially toward or away from the tire 40 in adirection parallel to the axis of rotation A of the tire. The upperrestraint ring 182U is supported and moved similarly relative to theupper cross member 134 and support 242U.

The controller 166 and control program determine the amount of restraintor displacement needed at the location 236 of the first harmonic softspot 232 of the tire 40 as a control parameter in operation 206. Thecontrol parameters are preferably determined by a look up table inoperation 206 as a function of the magnitude 238 of correction to beapplied to the tire 40 and other input parameters. The look up table canbe constantly updated to reflect the history of previously correctedtires. The amount of restraint is defined by the amount of axiallyinward deflection applied to a sidewall of the tire 40. For example, themaximum amount of desired deflection D2 at the hard spot may be 15millimeters as determined by the controller 166 and control program inoperation 258. The sidewalls of the tire 40 on the right side, as viewedin FIG. 7, each are deflected axially 15 millimeters inwardly. This maybe done manually or under controller 166 and control program directionand verified by digital output display 248R to indicate 15 millimetersof deflection D2. The minimum amount of restraint is applied to thesidewalls on the far left, as viewed in FIG. 7. For example, the minimumamount of restraint may be 0 to 5 millimeters deflection D1 as verifiedin the digital output displays 248L or may even be a gap of 0 to 10millimeters. It will be apparent that the restraint rings 182 are tiltedrelative to the mid-circumferential plane M of the tire 40 to be closertogether at the far right of the correction station 140, as viewed inFIG. 7. If a gap is initially provided, it will generally close by thesidewall contacting the restraint ring 182 as the tire 40 is inflated.

The maximum amount of deflection may be 15 millimeters in the axialdirection. This means that each sidewall of the tire 40 is deflected adistance D2 axially inwardly against the relatively low initialinflation pressure, such as 3 to 5 psi. The minimum amount of restraintmay be 0 to 5 millimeters of axial deflection D1 of the sidewall at thelocation 236 of the first harmonic soft spot 232 (FIG. 3). The inflationpressure of the tire 40 is then raised significantly to a predeterminedpressure above the recommended operating pressure of the tire, forexample 100 psi or 7 bars, and held for a predetermined hold time. Theminimum predetermined pressure is preferably in the range of two tothree times the operating pressure of the tire 40. The predeterminedhold time may be, for example, 10 seconds but will be considerablyshorter than a cure cycle period. The minimum predetermined hold time ispreferably at least one second. The input parameters as to amount ofdeflection, inflation pressure and hold time can be selected and variedby the controller 166 and control program in operations 258 (FIG. 14) asa function of the magnitude of uniformity characteristic correctionneeded, the size of the tire, the properties of the tire and theintended application of the tire.

This relatively high predetermined pressure forces the carcassreinforcing members 306 (FIG. 9) of the tire 40 to react to the elevatedinternal pressure and increase the tension in each carcass reinforcingmember which results in lengthening. This increased tension andlengthening, when held even for a relatively short period of time abovethe elastic limit of the carcass reinforcing member 306, as illustratedin FIG. 20, results in the permanent deformation L by stretching of thecarcass reinforcing members 306. The carcass reinforcing members 306which have no or minimal restraint at the soft spot 232 on the left sideof the correction station 140 are permanently deformed the greatestamount. Less permanent deformation occurs gradually in bothcircumferential directions towards the hard spot 234 located on theright side of the correction station 180° C. from the soft spot 232. Theleast amount of deformation occurs at the location of maximum restraintat the hard spot 234. The permanently longer each carcass reinforcingmember 306 gets relative to its prestretch length, the "harder" itbecomes in terms of radial force variation due to its permanentelongation. A belt restraint ring 280 (FIG. 8) may be optionallyprovided to counteract the relatively high inflation pressures so thatthe belt package 46 is not excessively expanded in the circumferentialdirection.

FIGS. 4 and 5 illustrate the same tire 40 after correction for firstharmonic radial force variation. It will be apparent that the relativemagnitude as defined by peak-to-peak magnitudes of the correspondingcomposite and first harmonic wave forms are dramatically lower in thewave forms of corrected tire 40 as illustrated in FIGS. 4 and 5 than inthe initial wave forms of the uncorrected tire as illustrated in FIGS. 2and 3. Also illustrated in FIG. 4 is a curve after the tire 40 has beenin service for a predetermined amount of time as would occur after, forexample, 1,000 miles of service. This illustrates that the uniformitycorrection is permanent.

Another physical representation of what actually occurs when the firstharmonic radial force variation of the tire 40 has been correctedaccording to the present invention is illustrated in FIG. 13. It isknown that radial runout of the tire 40 affects the radial forcevariation. Such a radial runout is exaggerated in FIG. 13, as the outercircumference 322 of the tire 40 in dashed line. The radius RR1 on theright side of the tire 40 in relation to the center of rotation 320 ofthe tire 40 established by the beads 42 is relatively smaller than theradius RR2 on the left side. The portion of the tire 40 at the farmostlocation to the right would be deemed to be the location 236 of the softspot 232 of the tire which would lend itself to first harmonic radialforce variation correction.

During correction according to the present invention, the radius RR1 isincreased over a rightmost portion 326 of the outer circumference 322 ofthe tire 40 to a radius RR3 due to the relatively greater elongation ofcarcass reinforcing members in the vicinity of the soft spot 232. Theradius RR2 is reduced to a radius RR4. The belt package 46 is relativelyinextensible and the outer circumference of the tire 40 does notincrease. However, the location of the entire tread or outercircumference of the tire shifts to the right, as viewed in FIG. 13.This radial runout correction allows the now relatively uniform radiiRR3, RR4 to establish new outer circumference 324 (solid line) relativeto the center of rotation 320 for the corrected tire 40. This radialrunout correction frequently reduces the magnitude of the first harmonicradial force variation a sufficient amount to be deemed acceptable.However, when the first harmonic radial force variation is caused bytire attributes other than radial runout, it may be necessary tointroduce a radial runout to reduce the magnitude of the first harmonicradial force variation.

What has actually taken place during the correction operation 258 (FIG.14) in this physical representation, is correction by introducing aradial runout to the tire 40. This introduced radial runout offsets thefirst harmonic radial force variation regardless of the attribute of thetire 40 producing the radial force variation. While the corrected radiiRR3, RR4 are not exactly equal necessarily, the resulting radial forcevariation (be it composite or first harmonic) is reduced during rotationof the tire 40.

The correction has been introduced over the portion 326 of the tire 40by maximally permanently elongating portions 302 of the carcassreinforcing members 306 located in both sidewalls of the tire 40 (FIGS.9 and 10). The portions 312 of carcass reinforcing members 306 in thesidewalls of the tire 40 that were minimally permanently elongated ornot elongated at all were restrained by the restraint rings 182 asdescribed above. For example, the restraint rings 182 would place themaximum amount of restraint and maximum deflection at the leftmostportion of the sidewall of the tire 40, as viewed in FIG. 13. Thisportion of the tire 40 corresponds to the location of the first harmonichard spot 234. At the same time, minimum restraint and minimumdeflection or even a gap would be allowed at the rightmost portion ofthe sidewall, as viewed in FIG. 13. This portion of the tire 40corresponds to the location 236 of the first harmonic soft spot 232.When the restrained tire 40 is inflated to a predetermined pressure, asdescribed above, and held for a predetermined time, the portions 302 ofthe carcass reinforcing members 306 in the minimally restrained portionsof the tire are permanently elongated by an amount greater than in themaximally restrained portions 312 of the tire.

The procedure described above corrects the first harmonic of the radialforce variation associated with the location 236 of the soft spot 232indicated by the signal generated by the controller 166. However, if thesecond, third, fourth or greater harmonics of radial force variation isdesired to be corrected, the location and number of minimum restraintsmust be varied on the sidewalls of the tire 40 during subsequentinflation and correction operations. For example, for the secondharmonic of radial force variation to be corrected based on the waveform illustrated in FIG. 3 the amount of minimum restraint would be attwo different locations 237 of second harmonic soft spots 233 from thelocation 236 of the first harmonic soft spot 232. Typically, the maximumamount of restraint as a function of the magnitude at the locationindicated by the signal generated by the controller 166 will likely beless for the second harmonic than for the first harmonic. The maximumrestraint can be maintained in the controller 166 and control program asa function of the second harmonic peak-to-peak magnitude. It should beapparent that higher order harmonics of the radial force variation wouldbe corrected in a manner similar to that described for the first andsecond harmonics.

Another correction option in operation 208 (FIG. 14) is that ofcomposite radial force variation correction. In operation 210 the hardspot 214 (FIG. 2) of the composite radial force variation of the tire 40is identified as well as its location 215 relative to a physicalreference on the tire. The location 216 of the composite soft spot 212is also identified in the controller 166 and control program. Thecontroller 166 and control program determine or read the compositepeak-to-peak magnitude which is represented by a distance 218 to beapproximately 7 daN. The magnitude 218 and the location 216 of the softspot 212 may be used as input parameters for the correction operation258 (FIG. 14) if the magnitude falls within a predetermined range ofmagnitudes deemed appropriate for correction. For example, the range maybe six daN to 12 daN.

It should be apparent, in the wave forms illustrated in FIGS. 2 and 3,that the locations 216, 236 of the respective soft spots 212, 232 may beoffset relative to one another. This results because the Fourieranalysis defines the locations of the soft spot and hard spot of, forexample, the first harmonic wave form as being 180° apart. Similar evenspacing of the respective adjacent soft and hard spots of the otherharmonic wave forms also occur. It should also be apparent that the softspot 212 of the composite wave form is not necessarily spaced 180° fromthe hard spot 214 but occurs as sensed during testing. For example, inthe composite wave form illustrated in FIG. 2, the soft spot 212 isspaced approximately 150° from the hard spot 214.

If composite radial force variation correction is desired, the location216 of the soft spot 212 of the composite radial force variation ispositioned at the far left hand side of the correction station 140, asviewed in FIG. 6. This positioning can be done by first making the tire40 so the soft spot 212 is located angularly from the physicalreference. A first order composite radial force variation correction isperformed as outlined in operation 258 (FIG. 14) and as described abovefor first harmonic correction. The correction involves permanentelongation of portions of carcass reinforcing numbers 306, preferably byincreasing the inflation pressure of the tire 40 considerably above therecommended operating pressure of the tire and holding that increasedpressure for a predetermined hold time.

The maximum amount of restraint for composite radial force variationcorrection should be at the composite hard spot 214 on the tire 40.However, for the composite wave form illustrated in FIG. 2, the location215 of the hard spot 214 is 150° away from the location 216 of the softspot 212. The maximum restraint of the "first harmonic" restraint rings182 will occur at the location 180° from the location 216 of thecomposite soft spot 212 when the restraint ring 182, described above, isused. A minimum amount of restraint, no restraint or a gap is applied tothe sidewalls of the tire 40 at the location 216 of the soft spot 212,217 indicated by the signal and known to the controller 166 at thecorrection station 140. Thus, some tradeoff in the location of maximumrestraint occurs due to the use of the first harmonic restraint rings182.

As an alternative embodiment, a restraint ring 380 (FIG. 21) can be usedwhich has a cupped segment 383 which is not in a plane containing theplanar surface 384. For example, the cupped segment 383 preferablyextends over a 90 degree arc length of the restraint ring 380. Thecupped segment 383 provides nonlinear restraint to the tire 40. Such acupped restraint ring 380 can be used to correct composite radial forcevariation as illustrated in FIG. 2, by relatively positioning the cuppedsegment 383 relative to a soft spot 212 or 217. With several (two forthe wave form illustrated in FIG. 2) different angular locations of therestraint ring 380 and associated inflation pressure cycles for the sametire 40, the composite radial force variation of the tire can beeffectively corrected. It is apparent that the shape of the surface ofrestraint ring 380, namely the number, size and position of segments383, can be selected to give any predetermined restraint ring shapewithin the scope of this invention. However, the maximum correction willstill occur at the soft spot 212 because minimal restraint (maximumcupping) can be applied at the location 216. Other restraint devicescould be developed to optimize the location of maximum restraint.

If the controller 166 and control program, as illustrated in FIG. 14,determine that the tire 40 is to be corrected for conicity in operation202, the location or side of the tire 40 requiring the correction isidentified in operation 204 to the controller. The location or side ofthe tire requiring correction is a function of the direction ofconicity. The parameters as to the location or side of the tire 40 andthe magnitude of correction required by the tire 40 are used by thecontroller 166 and control program in the correction operation 208.These parameters are input to operation 206 and stored for thecorrection operation 258 for each tire 40 to be corrected.

In order to correct conicity of the tire 40 in the correction station140 illustrated in FIG. 7 the following procedure is performed. If theside of the tire 40 to be corrected for conicity is located facingupwardly in the correction station 140, then no restraint will beapplied to the upwardly facing sidewall of the tire. The lower restraintring 182D is brought into engagement with the lower sidewall of the tire40. The lower restraint ring 182D is moved axially inwardly asubstantially equal amount over the entire planar contact surface of therestraint ring 182D. Thus, the lower restraint ring 182D is not tiltedand the upper restraint ring 182U does not engage the tire 40. However,it will be apparent that two restraint rings 182 could be used forconicity correction with different amounts of restraint used on thedifferent sidewalls of the tire 40, as described herein below.

When the proper amount of deflection or restraint has been applied tothe lower sidewall of the tire 40 by the restraint ring 182D, correctionfor conicity may be initiated. The internal pressure of the tire 40 isthen elevated to an amount sufficient to produce a desired permanentelongation in the carcass reinforcing members 306 in one sidewall of thetire. Such a pressure may be, for example, 100 psi or 7 bars. Thedeflection and elevated internal pressure is held for a relatively shortperiod of time, for example, for ten seconds. The tire 40 is thendeflated and the restraint removed from the lower sidewall of the tireand the tire is removed from the correction station 140. The conicitycorrection has occurred in the portions of the carcass reinforcingmembers in the upper sidewall of the tire 40 which was not restrained.All of the portions of the carcass reinforcing members in the uppersidewall of the tire were permanently stretched preferably by an equalamount. The belt restraint ring 280 may be used to keep the tread 62 ofthe tire 40 from moving axially during conicity correction.

It will be apparent that if the lower sidewall of the tire 40 as it isplaced in the correction station 140 needed correction, then the uppersidewall of the tire would be restrained by deflecting it axiallyinwards. It should also be apparent that depending on the amount andlocation of conicity desired to be corrected, that the restraint rings182D, 182U could both engage opposite sidewalls of the tire to applydiffering deflection based on the magnitude of correction desired. Thus,the inflation and hold procedure can take place and correct bothsidewalls by differing amounts. It will also be apparent that onerestraint ring 182 could be tilted if the magnitude of the conicitysignal to be corrected is not a constant amount circumferentially aroundthe tire 40.

If a conicity characteristic is to be corrected, the side of the tire 40needing the correction is identified to the controller 166 and controlprogram. No special angular orientation of the tire 40 is generallyneeded if a conicity characteristic is to be corrected. The side of thetire 40 needing correction and the amount or magnitude of correctionrequired must be known for conicity characteristic correction on thecorrection station 140 of the present invention.

The restraint rings 182 each preferably have a flat or planar surface260 (FIG. 8) for use in correction of the first harmonic or composite ofradial force variation or in correction of conicity. Each restraint ring182 has a radial length of engagement LE1 (FIG. 9) with the sidewall ofthe tire 40 which is a relatively small percentage (i.e. less than 25%of the section height SH (FIG. 8) of the tire. The edges 278 of therestraint ring 182 may be rounded to avoid sharp edges. The restraintring 402 may also have a radial length of engagement LE2 (FIG. 15) thatis a relatively large percentage (i.e. greater than 25% of the sectionheight SH of the tire 40.

If a restraint ring 380 (FIG. 21) is provided with a cupped or concavesurface in one or more locations, then other harmonics may be correctedduring one correction operation. Such a restraint ring 380 is describedabove and may have a cupped portion 383 over 90° of the surface 384(FIG. 23). This allows correction of, for example, first and secondharmonics of radial force variation when the soft spot of the secondharmonic is located away from the soft spot of the first harmonic. Theplacement of the restraint ring 380 against the tire 40 is determined bythe controller 166 to be optimal under program parameters.

The amount of permanent deformation to the carcass reinforcing members306 occurs by stretching a portion 302 or 312 of the carcass reinforcingmember which is preferably located in a sidewall of the tire beyond itselastic limit (FIG. 10). This may be done by stretching the cordpermanently in the range of 0.1 to 2 or 3 percent or some predeterminedamount as a function of the magnitude of uniformity characteristicdesired to be corrected, and the material of the carcass reinforcingmember. The results of a first harmonic linear correction by 5millimeters minimum restraint and 15 millimeters maximum restraint isillustrated FIG. 12. The tire 40 was exposed to 100 psi (7 bars) ofinternal pressure for ten seconds of hold time with a planar surfacerestraint ring 182. It has been observed that for a passenger car tire,one percent of permanent elongation of the carcass reinforcing member306 between the points 304 and 308 (FIG. 10) at the first harmonic softspot and zero percent at the hard spot results in approximately 10 daNof first harmonic radial force variation.

An alternate restraint device 388 is illustrated in FIG. 11. A portionof the sidewall of the tire 40 is restrained without a deflection. Therestraint device 388 comprises two portions 394 that contact the tire 40at two radial locations 390,392. These radial locations 390,392 contactthe outer surface of the sidewall of the tire 40. The portions 394 ofthe restraint device 388 are spaced equally from the equatorial plane E.The sidewall of the tire 40 has an unrestrained length 396 which isdeflected by the inflation pressure. The unrestrained length 396 has aminimum dimension associated with the hard spot and a maximum dimensionassociated with the soft spot. The unrestrained length 396 of therestraint device 388 varies circumferentially around the tire from thehard spot to the soft spot, as illustrated in FIG. 22. The carcassreinforcing members are permanently elongated during inflation a greateramount where the unrestrained length 396 has a larger dimension.

The restraint device 388 has interconnecting parts 398 so that theportions 394 in contact with the tire can act as one device. Thisrestraint device 388 allows the carcass reinforcing members to have adeflection 316 and a radius of curvature R4 which is smaller than theinitial unrestrained radius of curvature R1 under the influence ofinflation pressure.

FIG. 15 illustrates a flat surface restraint ring 402 having a radiallength of engagement LE2 which is a relatively large percentage of thesection height SH of the tire for a radial length of engagement. Thisyields a radius of curvature R3 which is less than the initial radius ofcurvature R1. FIG. 16 corresponds to a schematic illustration of whatoccurs to the portion 422 of the carcass reinforcing member duringcorrection under relatively high pressure with the restraint ring 402.

FIGS. 17 and 18 similarly schematically illustrate an alternative methodand apparatus for use without an inflation pressure increase in the tire40. The devices 502, 504, 506 mechanically stretch portions 512 of thecarcass reinforcing member axially outwardly beyond its elastic limit.FIG. 19 is another schematic illustration of mechanically stretching aportion 602 of the carcass reinforcing member beyond its elastic limit.This is done by radially stretching the portion 602 of the carcassreinforcing member between the upper and lower attachment points 604,606 in the sidewall of the tire 40. Deflection 608 of the portion 602results. This stretching could be accomplished by moving point 606radially inward, and point 604 radially outward or by moving point 604radially outward. It should be apparent that stretching of the portionof carcass reinforcing members could be accomplished by a combination ofmechanical stretching and by inflation pressure stretching.

The following is an example of a radial force variation correctionperformed in accordance with the method and apparatus of the presentinvention.

    ______________________________________                                        TEST RESULTS OF CORRECTED TIRES                                               3mm Maximum Restraint Deflection                                              6mm GAP Minimum Restraint                                                     10 Second Hold Time                                                                 Before    After              Treatment                                  Tire  Correction                                                                              Correction                                                                              Improvement                                                                            Pressure (bar)                             ______________________________________                                        1     3.7    daN    2.0  daN  1.7   daN  7.5                                  2     4.6           2.3       2.3        8.0                                  3     5.4           2.5       2.9        8.5                                  4     3.3           1.5       1.8        7.25                                 5     5.1           2.0       3.1        8.25                                 6     2.8           0.8       2.0        7.0                                  7     4.7           2.3       2.6        8.0                                  8     4.9           2.3       2.6        8.0                                  9     4.2           1.2       3.0        7.75                                 10    6.0           1.8       4.2        8.5                                  AVG   4.47          1.87      2.60                                            ______________________________________                                    

The tire used for test purposes was a Michelin® 205/70R15 XZ4 tire. Itcan be seen that a 58 percent average reduction of first harmonic radialforce variation in the sample has occurred. This is a significantportion of the first harmonic radial force variation and the tire 40 socorrected will provide a dramatically improved ride when it is on thevehicle than if it had not been corrected. The correction occurredwithout grinding of the tire 40 and in a relatively short period oftime.

From the above description of preferred embodiments of the invention,those skilled in the art will perceive improvements, changes andmodifications. Such improvements, changes and modifications within theskill of the art are intended to be covered by the appended claims.

Having described preferred embodiments of the invention, what is claimedis:
 1. A method for reducing the magnitude of a uniformitycharacteristic in a cured tire, said method comprising the stepsof:determining a location on the tire to correct; and introducing aradial runout to the tire as a function of the determined location tooffset the uniformity characteristic and reduce the magnitude of aresulting uniformity characteristic to below a minimum thresholdmagnitude.
 2. The method set forth in claim 1 wherein said tire hascarcass reinforcing members said introducing step includes permanentlyelongating a portion of at least one carcass reinforcing member in asidewall of the tire.
 3. The method set forth in claim 2 wherein saidpermanently elongating step includes inflating the tire to apredetermined pressure.
 4. The method set forth in claim 3 furtherincluding restraining at least a portion of a sidewall of the tire at asecond location other than the determined location to correct and tolimit the elongation of the carcass reinforcing members at the secondlocation.
 5. An apparatus for reducing the magnitude of a uniformitycharacteristic in a cured tire, said apparatus comprising:means fordetermining a location on the tire to correct; and means for introducinga radial runout to the tire as a function of the determined location tooffset the uniformity characteristic and reduce the magnitude of aresulting uniformity characteristic to below a minimum thresholdmagnitude.
 6. The apparatus set forth in claim 5 wherein said tire hascarcass reinforcing members said introducing means includes means forpermanently elongating a portion of at least one carcass reinforcingmember in a sidewall of the tire.
 7. The apparatus set forth in claim 6wherein said permanently elongating means includes means for inflatingthe tire to a predetermined pressure.
 8. The apparatus set forth inclaim 7 further including means for restraining at least a portion of asidewall of the tire at a second location other than the determinedlocation to correct and to limit the elongation at the second location.